Electromagnet coil assembly



Dec. 25, 1956 E. A. BOGUE ET AL 2,775,742

ELECTROMAGNET COIL ASSEMBLY Filed March a, 1952 United States Patent ELECTROMAGNET COIL ASSEMBLY Edward A. Bogue, South Bend, Ind., and CharlesW. Musser, Niles, Mich., assignors to ETC, Inc., Niles, Mich., a corporation of Illinois Application March 6, 1952, Serial No. 275,096

4 Claims. (Cl. 33683) This invention relates to an electromagnet coil assembly and more particularly to an assembly of this sort which includes a casing or housing of magnetizable material that serves as a protective enclosure for the coil and provides an effective magnetic circuit.

An object of this invention is to provide a magnet coil assembly in which a metal housing serves as a container for an assembled coil and terminal unit and provides space for thermo-pla'stic insulating material which not only moisture-proofs the coil, but acts to protect and secure certain parts of the assembly.

A further object of our invention is the provision of a magnet coil assembly including a coil and terminal subassembly having parts adapted to be supported and held in place during operations of assembly with a container which holds thermo-plastic insulating material and provides an outer housing for the coil.

Other objects and advantages of the invention will be apparent from the following description and the accompanying drawings in which similar characters of reference indicate similar parts throughout the several views.

Referring to the one sheet of drawings:

Fig. 1 is a perspective View of an embodiment of the electromagnet coil assembly of this invention;

Fig. 2 is a perspective view of a preferred spool, coil, and terminal sub-assembly adapted to use with a magnetic casing and thermoplastic insulating material to constitute the assembly illustrated in Fig. 1;

Fig. 3 is a side elevational view, partly in section and having parts separated to illustrate details of the subassembly depicted in Fig. 2;

Fig. 4 is a longitudinal vertical section taken through the complete assembly illustrated in Fig. 1;

Fig. 5 is a transverse sectional view of the complete assembly taken substantially on the line 5-5 of Fig. 4 and in the direction of the arrows; and

Fig. 6 is a fragmentary longitudinal sectional view similar to a portion of Fig. 4, and modifications of structural features of the electromagnet coil assembly of our invention.

In the exemplary adaptation of the invention pictured in the drawings for illustrative purposes, our electromagnet coil assembly, in its general aspects, is composed of a spool or bobbin 10, a coil 11 wound thereon, terminals 12 and 13 for the connecting leads to the coil, a housing or casing 14 of magnetizable metal which encloses the spool and coil, spaced and split tubes 15 and 16 of magnetizable metal which fit within the spool and project through aligned openings in end walls 17 and 18 of the casing 11, and a mass of insulating material 19 which fills the space between the casing and the spool and coil and partially covers the terminals.

The spool 10, in the disclosed structure, is integrally molded of an insulating material, such as nylon, and has end flanges 20, as shown in Fig. 5, which are generally of rectangular shape with rounded corners to fit within the casing 14 with small amounts of clearance. The cas- 2,775,742 Patented Dec. 25, 1956 ing 14 and tubes 15 and 16 are made of highly permeable and readily demagnetizable metal such as soft iron. The coil 11 is wound of wire that has an insulating coating such as enamel. Each of the terminals 12 and 13, in the disclosed structure, is composed of an inner part 21 made of a highly conductive metal, such as copper, and an outer part 22 made of a high-strength metal, such as iron or steel. The insulating material 19 is a thermoplastic insulating material such as a suitable tar, wax, resin, or a mixture of resin and mica particles.

The coil 11 has an end lead 23 which comes from the inside of the winding to the outside thereof between the folds of an adhesive insulating strip 24 which is doubled upon itself to enclose the end lead 23, with the adhesive face of one half the length of the strip against the adhesive face of the other half. This end lead extends to the terminal 13. The folded insulating strip 24 extends along a large portion of the length of the spool 10, and then radially outward along one spool flange 20 for a short distance beyond the outer surface of the coil 11, whereby that strip is anchored by the inner layer of the winding and is held between the end turns of the coil and the spool flange 17. The blind or closed end of the folded strip 24 on the spool 10 is within the coil 11, and the free or open ends are on the exterior of the coil 11. In the application of the coil to the spool, the folded strip 24, with the coil end lead 23 between the folded. sides thereof, is laid against the spool as shown, and then the coil is wound. The folded strip 24 is held on the spool in preparation for the winding operation by an adhesive insulating strip 25 which extends partially about the spool 10. The coil 11 also has an outer end lead 26 which is brought from the exterior of the winding over an adhesive band 27 which extends partially around the coil and under an adhesive band 28 which completely encompasses the coil. Both bands 27 and 28 have their adhesive sides facing the coil. 1

An insulating saddle 29, which in the present instance is made of a spun glass cloth impregnated with plastic, extends along the outer surface of the coil 11 between a portion of the end lead 26 and the winding, and between the winding and the outer end portion of the folded strip 24 and its included end lead 23. The saddle 29 is secured to the coil by the adhesive band 28 and also by an adhesive band 30, which latter band encompasses the winding and extends over the exterior end portion of the folded strip 24. The purpose of the insulating saddle 29 is to insulate the coil end leads 23 and 26 and their terminals from the outer turns of the coil 11.

Fig. 3 illustrates a terminal sub-assembly as it is about to be applied to the coil assembly. This terminal subassembly comprises the terminals 12 and 13, a narrow and relatively stiff terminal strip 31 of insulating material, and a pair of hollow rivets 32 which go through the terminals and the terminal strip to secure the terminals to the strip. The coil ends 23 and 26 extend through the hollow rivets 32 and are metallically bonded thereto by soldering or the like as indicated at 33 in Fig. 4. The terminal sub-assembly is secured to the coil outside of the insulating saddle 29 by an adhesive band 34 which extends completely around the coil.

The coil and terminal assembly including spool 10, coil 11, insulating saddle 29, terminal strip 31, and terminals 12 and 13, when completed as described, appears as shown in Fig. 2, and is ready to be placedin the casing 14 of magnetizable metal. The split tubes 15 and 16 of magnetizable metal are inserted from opposite ends of the casing and extend into the spool as shown in Fig. 4. The insulating material 19, when heated to a liquid, semiliquid or plastic state, is poured into the casing to a depth such that it not only fills the spaces between the casing and coil assembly, but also covers the terminal strip 31 and portions of the terminals 12 and 13. Thereafter the insulating material hardens to provide a moisture-proof seal for the coil assembly and securely to retain the terminal strip assembly in place with only the ends of the terminals 12 and 13 exposed for making electrical connections thereto.

In the modification of our invention which is illustrated in Fig. 6, the insulating saddle is omitted, and the terminal sub-assembly, including terminals 12 and 13, terminal strip 31, and rivets 32, is held in spaced relationship to the coil 11 by the spool flanges 20. In the disclosed structure, the flanges have notches 35 which receive the ends of the terminal strip 31, thereby to hold the terminal sub-assembly away from the winding, as well as in a manner to prevent lateral movement thereof with respect to the spool 10 and the coil 11. When the insulating material 19 is applied, it fills the space between the terminal strip 31 and the coil 11. In this modification care should preferably be taken to extend the length of the folded strip 24 so that the open end thereof is directly beneath the rivet 32 of the terminal 13, in order that the exterior portion of the end lead 23 is kept away from the outer turns of the coil.

From the foregoing description and by reference to the accompanying drawings, it may be understood that we have provided a protected and moisture-proofed coil assembly including a coil and terminal strip sub-assembly having parts secured in position for assembly operations and finally anchored or immobilized within a housing by thermo-plastic insulating material, In one disclosed modification, a saddle of insulating material insures insulating separation between the terminals and the coil, while in the other form, the separation of the terminals from the coil is insured by mounting the terminal strip on the ends of the spool upon which the coil is wound.

While We have illustrated a preferred embodiment of our invention, many modifications may be made without departing from the spirit of the invention, and We do not Wish to be limited to the precise details of construction set forth, but desire to avail ourselves of all changes within the scope of the appended claims.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent of the United States is:

1. An assembly comprising a spool made of insulating material; a coil wound thereon, a saddle of plasticimpregnated glass cloth extending along the exterior of one side of the coil; first and second insulating bands encompassing the coil to secure the saddle in place thereon; a sub-assembly composed of a terminal strip of insulating material extending along the coil over the saddle, a pair of terminals secured to the terminal strip by hollow rivets which have the ends of the coil extended therethrough and soldered thereto; and a third insulating band encompassing the coil and the terminal strip to secure said subassembly to the coil.

2. An electromagnet coil assembly comprising a spool made of insulating material, a coil wound on the spool, input and output terminals connected to the coil, a housing of magnetizable metal containing the spool and coil, said housing having end walls and an open top, slotted magnetic tubes snugly fitting within the spool and extending through the end walls of the housing, and thermoplastic insulating material filling the space between the coil, the spool and the housing, said terminals extending outwardly from the said insulating material through the open top of the housing.

3. An electromagnet coil assembly comprising a spool made of insulating material, a coil wound on the spool, a terminal strip of insulating material extending along one side of the coil, a pair of terminals secured to the strip and electrically connected to the ends of the coil, a housing of magnetic material having an open side and containing the spool and the coil with the terminal strip at the open side of the housing, a tubular element of magnetic material fitting within the spool and extending through an end wall of the housing, and thermo-plastic insulating material filling the space between the coil and the housing and covering the terminal strip and portions of the terminals to seal the assembly and secure its parts together.

4. An electromagnet coil assembly as specified in claim 3, and wherein the spool has end flanges which fit adjacent and conform substantially to the interior of the end walls of the housing.

References Cited in the file of this patent UNITED STATES PATENTS 1,702,159 Grunow Feb. 12, 1929 1,836,948 Anderson Dec. 15, 1931 1,939,808 Freeland Dec. 19, 1933 2,194,703 Kater Mar. 26, 1940 2,249,057 Stahl July 15, 1941 2,264,832 Ensign Dec. 2, 1941 

